Search found 2797 matches

by tomfid
Thu Oct 17, 2019 2:15 am
Forum: Vensim
Topic: Error in "GET XLS DATA" when I run a model that previously worked fine
Replies: 6
Views: 241

Re: Error in "GET XLS DATA" when I run a model that previously worked fine

I've had the same problem recently on 1 out of 3 systems. I think it may be an Excel change. Switching from GET XLS to GET DIRECT may help.
by tomfid
Wed Oct 16, 2019 6:19 pm
Forum: Vensim
Topic: Problem with Command Script using GET XLS CONSTANTS
Replies: 12
Views: 388

Re: Problem with Command Script using GET XLS CONSTANTS

How many datasets do you have? You could create a data variable for each, then switch the data used numerically, rather than switching the source name. It's a little inefficient, but it won't matter unless the dataset is large.
by tomfid
Wed Oct 16, 2019 4:19 pm
Forum: Ventity
Topic: Published Research using Ventity
Replies: 4
Views: 322

Re: Published Research using Ventity

Cool. I can't see through the paywall - is this a hybrid, with CLDs in Vensim and the model in Ventity?
by tomfid
Wed Oct 16, 2019 4:05 am
Forum: Vensim
Topic: How to specify a vector of data in Vensim P.L.E. 8.0.4. x64
Replies: 4
Views: 214

Re: How to specify a vector of data in Vensim P.L.E. 8.0.4. x64

I should add that Ventity has detail and data capability, and is currently free for academic use.
by tomfid
Tue Oct 15, 2019 2:27 pm
Forum: Vensim
Topic: Improving the modelling of annual decisions used for optimization
Replies: 6
Views: 281

Re: Improving the modelling of annual decisions used for optimization

Generally, yes. VECTOR LOOKUP is potentially better because it interpolates, so you could have fewer points than there are time steps in the model.

A feedback-based decision rule is still superior.
by tomfid
Mon Oct 14, 2019 6:35 pm
Forum: Vensim
Topic: The question about Find Zero function
Replies: 5
Views: 214

Re: The question about Find Zero function

I don't know what any of this means, but with a corrected expression it works:
FIND ZERO 2.mdl
(9.73 KiB) Downloaded 20 times
by tomfid
Mon Oct 14, 2019 6:25 pm
Forum: Ventity
Topic: Published Research using Ventity
Replies: 4
Views: 322

Re: Published Research using Ventity

There isn't too much yet, due to the lags in adoption and publication, but if you point us to something, we'd be happy to feature it, and perhaps to start a page on the Ventity site.
by tomfid
Mon Oct 14, 2019 5:34 pm
Forum: Vensim
Topic: The question about Find Zero function
Replies: 5
Views: 214

Re: The question about Find Zero function

To clarify, the equation in the model uploaded appears to differ from the one in your initial post. The model has no solution; the original equation might.
by tomfid
Mon Oct 14, 2019 5:24 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 1724

Re: sensitivity analysis (vensim)

We're working on it, but I'm not sure whether it'll be done by end of year. The speedup is more than noticeable if you have a many-core machine. Older workstations with 16 or more cores are now readily available at dirt cheap prices. We'll keep you posted as this evolves.
by tomfid
Mon Oct 14, 2019 5:21 pm
Forum: Vensim
Topic: The question about Find Zero function
Replies: 5
Views: 214

Re: The question about Find Zero function

I think the immediate problem is that you have the initial guess (initial x) set to 0. If the function's first execution is invalid, it can't proceed with a search.

If you set initial x = 1, it runs, but there's no solution to the equation, so it still fails to converge.
by tomfid
Mon Oct 14, 2019 4:00 pm
Forum: Vensim
Topic: Improving the modelling of annual decisions used for optimization
Replies: 6
Views: 281

Re: Improving the modelling of annual decisions used for optimization

You need to specify the subscript dimension:
0<=timevalues[timerange]<=150
by tomfid
Mon Oct 14, 2019 2:52 pm
Forum: Vensim
Topic: Noise Seed in Venapp
Replies: 4
Views: 195

Re: Noise Seed in Venapp

Hossein is correct - the sensitivity seed can't be changed programmatically. We should change that. A workaround is to provide several different vsc files with different seeds. Another possibility is to use the vsc file to vary noise seed, and generate the distributions for the target variables insi...
by tomfid
Fri Oct 11, 2019 12:42 pm
Forum: Vensim
Topic: Noise Seed in Venapp
Replies: 4
Views: 195

Re: Noise Seed in Venapp

Add NOISE SEED to the model and change it with SETVAL.
https://www.vensim.com/documentation/noise_seed.htm
by tomfid
Thu Oct 10, 2019 4:52 pm
Forum: Vensim
Topic: How to specify a vector of data in Vensim P.L.E. 8.0.4. x64
Replies: 4
Views: 214

Re: How to specify a vector of data in Vensim P.L.E. 8.0.4. x64

Correct. Arrays are a Pro/DSS feature only.

PLE is really focused on learning about dynamics - it doesn't do detail complexity and data.

If you email us, we'd be happy to send you an evaluation license for Pro/DSS for testing.
by tomfid
Thu Oct 10, 2019 1:46 pm
Forum: Vensim
Topic: Giving time series data
Replies: 12
Views: 1308

Re: Giving time series data

Are you talking about the units or granularity of the data? Generally it's always better to use the finest time scale you can, given the time step of the model.
by tomfid
Wed Oct 09, 2019 7:23 pm
Forum: Vensim
Topic: Negative Levels
Replies: 6
Views: 204

Re: Negative Levels

This is puzzling ... we've never dropped Euler's method, and there haven't been any changes to the sim engine in v8. If you have a model demonstrating the problem, or a screenshot, we'd be very interested to explore the issue.
by tomfid
Wed Oct 09, 2019 5:22 pm
Forum: Vensim
Topic: Giving time series data
Replies: 12
Views: 1308

Re: Giving time series data

Vensim will be looking for time formatted as a decimal year.
by tomfid
Wed Oct 09, 2019 1:32 pm
Forum: Vensim
Topic: Problem with Command Script using GET XLS CONSTANTS
Replies: 12
Views: 388

Re: Problem with Command Script using GET XLS CONSTANTS

The .cin file trick also fails.
by tomfid
Wed Oct 09, 2019 1:28 pm
Forum: Vensim
Topic: Problem with Command Script using GET XLS CONSTANTS
Replies: 12
Views: 388

Re: Problem with Command Script using GET XLS CONSTANTS

Note the provision in the docs for SETVAL: If you are using the SETVAL command to set a string variable do not include the surrounding single quotes. For example: SIMULATE>SETVAL|productname:IS:Metronone However, that alone is not sufficient to resolve the problem - it still seems to fail silently.
by tomfid
Fri Oct 04, 2019 3:23 pm
Forum: Vensim
Topic: sensitivity analysis (vensim)
Replies: 35
Views: 1724

Re: sensitivity analysis (vensim)

There's a little advice on speed here: https://metasd.com/2011/01/optimizing-vensim-models/ One item that's not mentioned there is that restricting the savelist helps. We have an experimental version that does parallel multicore execution, which would reduce your simulation time by a factor of the n...
by tomfid
Thu Oct 03, 2019 2:47 pm
Forum: Vensim
Topic: Improving the modelling of annual decisions used for optimization
Replies: 6
Views: 281

Re: Improving the modelling of annual decisions used for optimization

There are two options: 1. Replace the IF THEN ELSE structure with a VECTOR LOOKUP over time (I think the sample model for VECTOR LOOKUP illustrates this). Then you will have an array of time points, like decisionTime : (t1-t10) with gValue[decisionTime] = 3.5, 2.4, 1.9, 4.2 ... You can then specify ...
by tomfid
Tue Oct 01, 2019 5:48 pm
Forum: Vensim
Topic: Help - remove lines
Replies: 4
Views: 170

Re: Help - remove lines

In a custom graph, change the x-division and y-division settings.

For the graph tool, you can change the global setting on the Scaling tab of the Control Panel.
by tomfid
Tue Oct 01, 2019 5:26 pm
Forum: Vensim
Topic: Help - remove lines
Replies: 4
Views: 170

Re: Help - remove lines

Presumably you want to remove all but one. :) Without a legend, it's hard to be sure what this is. You need to do one of the following: - unload datasets using the Control Panel's datasets tab - deactivate subscripts using the Subscript Control - edit the custom graph definition using the Control Pa...
by tomfid
Sat Sep 28, 2019 9:01 pm
Forum: Ventity
Topic: Units (Millions and Billions)
Replies: 8
Views: 417

Re: Units (Millions and Billions)

Got it - thanks! I'll put in a ticket and we'll investigate.